The present invention relates generally to textile machines of the type used for wet processing of a traveling length of textile material and to methods of wet processing textile materials utilizing such machines. More particularly, the present invention relates to textile wet processing machines and methods wherein an indeterminate length of textile material travels sequentially through a series of material processing chambers and to a means and methodology for controlling the relative lengths of the textile material potions within the respective chambers.
Various types and forms of machines are known and in use in the textile industry for performing diverse finishing operations by the application of a liquid treatment to the textile material, such machines and methods of operation commonly being referred to broadly as wet processing. One common type of wet processing operation to which textile fabrics particularly are subjected is a washing operation, typically performed following a preceding wet processing operation for purposes of removing and/or neutralizing excess treating liquid remaining in or on the fabric from the previous operation. For example, a washing operation is typically performed on a textile fabric subsequent to a bleaching operation in order to completely remove bleach remaining in the fabric and to neutralize the fabric.
Conventional textile washing apparatus of differing constructions are known. In one form of such apparatus, the textile material to be washed is transported in sequence through a series of liquid containment chambers, typically by means of a lifter reel and liquid jet nozzle arrangement disposed between the chambers. The chambers are essentially separate from one another so that the fabric is subjected to a progressive cleaning of bleach or other liquid treatment compositions as the fabric advances from one chamber to the next.
One of the difficulties experienced in the on-going commercial operation of such textile washing apparatus is the maintenance of essentially the same quantity of fabric in each successive chamber, which is desirable from an operational standpoint in order to ensure that the fabric is subjected to the optimal degree of washing in each chamber and also from a safety and quality control standpoint in order to prevent the extreme occurrence that one or more chambers become substantially depleted of fabric which could ultimately result in severe damage to the fabric. While theoretically the setting of the several lifter reels and liquid jet assemblies between the successive chambers to operate at constant uniform speeds should achieve a balance of essentially the same quantity of fabric in each chamber, uncontrollable operational variables which routinely occur over the course of the washing process, e.g., sporadic slippage of the fabric on the lifter reels, random tangling of the fabric at different locations from chamber to chamber, the differential action of the jetted liquid in propelling the fabric depending upon the orientation of the fabric as it passes through the liquid jet assemblies, and changes in fabric type and weight from one fabric lot to the next, still causes imbalances to occur in the amount of fabric from chamber to chamber.
Several different forms of control systems have been proposed and implemented to address the objective of maintaining a generally uniform quantity of fabric in each of the plural chambers of such washing machines. In one form of control system, a physical switch is provided in each chamber at a predetermined elevation above the bottom of the chamber to be actuated in the event an excessive quantity of fabric accumulates within the chamber and, in turn, to initiate an appropriate change in the operation of the apparatus to alleviate the excess accumulation of fabric. Disadvantageously, however, the presence of such a physical switch presents the risk of unintended contact with the fabric which can produce tangling in the fabric or even cause damage to the fabric as a result of snagging on the switch.
An alternative form of washer control system utilizes a load cell in each chamber to at least periodically measure the weight of fabric momentarily present within each chamber so that a comparison can be made and appropriate corrective action taken, if necessary. Unfortunately, however, such a load cell-based system can be subject to inaccuracies because the load cell necessarily is weighing the entire contents of the chamber, which includes both the fabric itself and the washing liquid present within the chamber. Hence, fabric imbalances may not be recognized if offsetting imbalances in the amount of liquid in each chamber also occur at the same time. Conversely, imbalances in the amount of liquid from one chamber to the next can cause the control system to incorrectly detect a non-existent imbalance in the comparative quantities of fabric.